I. Field
The following description relates generally to wireless communication systems, and more particularly to providing flow control for a mobile device.
II. Relevant Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, Advanced LTE systems (LTE-A), and orthogonal frequency division multiple access (OFDMA) systems.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, Advanced LTE systems (LTE-A), and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A MIMO system supports a time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point.
For current LTE systems there exists no protocol or methodology to flow control the base station or network (NW) side. However, flow control may be required in a plurality of scenarios, such as when the mobile device or user equipment (UE) is not able to process high data rates (e.g., when user applications or tasks are running on the UE and are running out of memory). Present solutions typically address such scenarios by blindly dropping the transport blocks or Radio Link Control (RLC) Protocol Data Units (PDUs) received on the downlink (DL) (as if the RLC PDUs were never received) or selectively dropping media access control (MAC) Service Data Units (SDUs) based on the priority or Quality of Service (QOS) or Radio Bearer (RB) type (whether DRB or SRB) and then relying on RLC level re-transmissions later. Unfortunately, such conventional methods cause inefficiencies and wastage of over the air bandwidth and potentially extra transmission power on the DL side.